Prior art semiconductor device packages are fabricated in a sandwich mold configuration wherein the semiconductor device is encapsulated forming a package on both sides of the die. When the package is cooled after the molding process, the larger molded package tends to curl, which results in a defective or unusable device. Also, if the package has any minute openings or cracks that allow moisture to penetrate to the elements of the semiconductor device, delamination of the semiconductor die can occur, which will render the device defective, or will cause the device to have a reduced operating life. Furthermore, the use of a mold to construct the package increases the height and area of the package significantly.
A composite package assembly, such as disclosed in the aforementioned copending patent applications, is formed with a rigid lead frame and a thin flexible tape-like structure. The tape-like structure is configured with lead fingers that are connected to leads of the lead frame. The semiconductor assembly, which includes bond wires, is encapsulated using a two section mold that requires a number of molding steps to encompass the semiconductor device with the lead frame, tape-like structure, bond wires and conductive leads.
Conventional semiconductor molded packages which are standard in the semiconductor industry accommodate up to 160 conductive leads, which typically are spaced between 50 and 25 milli-inches from center to center. As the number of leads are increased, the number of bond wires that connect to the leads are increased accordingly. The increase in bond wires results in a larger package.
A major objective of the semiconductor industry is to make semiconductor devices with more conductive leads and yet to have a more compact package. With a more compact package, semiconductor die with more die pads can be used, which requires closer spacing of the leads of the semiconductor assembly. As a result, higher circuit operating speeds can be realized with improved operating reliability.